No abstract

Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal cancers, in part, due to resistance to both conventional and targeted therapeutics. Tumor necrosis factor-Related Apoptosis-Inducing Ligand (TRAIL) directly induces apoptosis through engagement of cell surface Death Receptors (DR4 and DR5), and has been explored as a molecular target for cancer treatment. Clinical trials with recombinant TRAIL and DR-targeting agents, however, have failed to show overall positive outcomes. Herein, we identify a novel TRAIL resistance mechanism governed by Hu antigen R (HuR, ELAV1), a stress-response protein abundant and functional in PDA cells. Exogenous HuR overexpression in TRAIL-sensitive PDA cell lines increases TRAIL resistance whereas silencing HuR in TRAIL-resistant PDA cells, by siRNA oligo-transfection, decreases TRAIL resistance. PDA cell exposure to soluble TRAIL induces HuR translocation from the nucleus to the cytoplasm. Furthermore, it is demonstrated that HuR interacts with the 3′-untranslated region (UTR) of DR4 mRNA. Pre-treatment of PDA cells with MS-444 (Novartis), an established small molecule inhibitor of HuR, substantially increased DR4 and DR5 cell surface levels and enhanced TRAIL sensitivity, further validating HuR’s role in affecting TRAIL apoptotic-resistance. NanoString™ analyses on the transcriptome of TRAIL-exposed PDA cells identified global HuR-mediated increases in anti-apoptotic processes. Taken together, these data extend HuR’s role as a key regulator of TRAIL-induced apoptosis. Implications Discovery of an important new HuR-mediated TRAIL resistance mechanism suggests that tumor-targeted HuR inhibition increases sensitivity to TRAIL-based therapeutics and supports their re-evaluation as an effective treatment for PDA patients.

sion is a major chronic disease whose molecular mechanisms remain poorly understood. We compared neuroanatomical patterns of microRNAs in the brain stem of the spontaneous hypertensive rat (SHR) to the Wistar Kyoto rat (WKY, control). We quantified 419 wellannotated microRNAs in the nucleus of the solitary tract (NTS) and rostral ventrolateral medulla (RVLM), from SHR and WKY rats, during three main stages of hypertension development. Changes in microRNA expression were stage-and region-dependent, with a majority of SHR vs. WKY differential expression occurring at the hypertension onset stage in NTS versus at the prehypertension stage in RVLM. Our analysis identified 24 microRNAs showing time-dependent differential expression in SHR compared with WKY in at least one brain region. We predicted potential gene regulatory targets corresponding to catecholaminergic processes, neuroinflammation, and neuromodulation using the miRWALK and RNA22 databases, and we tested those bioinformatics predictions using high-throughput quantitative PCR to evaluate correlations of differential expression between the microRNAs and their predicted gene targets. We found a novel regulatory network motif consisting of microRNAs likely downregulating a negative regulator of prohypertensive processes such as angiotensin II signaling and leukotriene-based inflammation. Our results provide new evidence on the dynamics of microRNA expression in the development of hypertension and predictions of microRNA-mediated regulatory networks playing a region-dependent role in potentially altering brain-stem cardiovascular control circuit function leading to the development of hypertension.hypertension; microRNA; neuroinflammation; angiotensin II; brain stem HYPERTENSION IS A MAJOR CHRONIC disease worldwide, affecting about 50 million adults in the United States alone. It is a multiorgan disease and a major cause of heart failure, coronary heart disease, atrial fibrillation, stroke, and end-stage renal disease, and it has an enormous economic impact. About 90 -95% of cases are "essential" with no known medical cause (11). Moreover, only about a third of hypertensive patients have their blood pressure fully controlled (11). A significant and increasing population (ϳ25%) of hypertensive patients is drug resistant. There remains an unmet need for antihypertensive therapy.In the context of the recent discovery of novel lines of therapeutic interventions involving approaches to modulate microRNA we decided to elucidate changes in microRNA levels during the development of spontaneous hypertensive rat (SHR) hypertension. The recent explosion in microRNA research has produced new computational and experimental approaches for studying microRNA functions in cell culture and in vivo, which we take advantage of here. MicroRNAs are an abundant class of small (ϳ22 nt) endogenous noncoding RNAs that direct posttranscriptional regulation of gene expression. There is ample evidence that dysregulation of microRNAs is associated with the pathogenesis of human diseases, in...

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